The invention relates to devices for preventing piracy (by unauthorized receivers) of television programs on "premium channels".
A number of cable television companies provide several kinds of service, one kind of service being referred to as "basic service" and another kind being referred to as "premium service". Drop cables coupled to a main cable are routed into a subscriber's residence and are coupled to the antenna inputs of a subscriber's television set. The "basic service" allows the subscriber to see high quality images on his television set for certain predetermined channels. Encoded program signals for other channels, referred to as "premium channels", are conducted on the same drop cables to the subscriber's television set. However, the resulting images that appear to a subscriber who is not authorized to receive the premium channels appear to be obfuscated. If a subscriber to the basic service pays an additional subscription fee for authorization to receive the premium channels, a decoding or filtering device is coupled between the subscriber's drop cable and the antenna inputs of his television set. The decoding or filtering device causes clear, unobfuscated images of the program on the premium channels to appear on the screen of the television set when the subscriber " tunes in" to premium channels.
A number of electronic devices have been devised by electronics amateurs and others to decode premium channel program signals that have been encoded or otherwise obfuscated, thereby allowing one who subscribes only to the basic service to watch the premium channels without paying the subscription fee therefor. In some cases, the decoding devices can even allow individuals who do not subscribe to the basic service to "pirate" the premium channel programs. Low cost premium channel decoding devices have been widely sold by certain electronics companies, making it very easy for many individuals to watch programs on premium channels without payment of the premium channel subscription fee. The widespread piracy of premium channel program signals obviously reduces the amount of revenue collected by cable television companies, and thereby increases the cost of premium channel service to those honest subscribers who pay the premium channel subscription fee. This situation inevitably has slowed the growth of cable television services and has reduced the availability of high quality cable television services to the public.
Thus, there is presently an unmet need for a piracy prevention device for cable television systems that can effectively frustrate the efforts of electronically skillful would-be pirates to obtain, without authorization, premium channel programs intended to be available only to authorized subscribers.
Therefore, it is a primary object of the invention to provide a piracy prevention device and method for preventing even electronically skilled would-be pirates from obtaining a sufficient amount of information from premium channel program signals to enable the would-be pirates to obtain acceptable images of premium channel programs.
Past experience has proved that persons skilled in the electronics art often are highly ingenius at finding ways of accurately decoding or otherwise recovering obfuscated premium channel program signals that enable such persons to obtain acceptable images of premium channel programs and thereby avoid paying the subscription fee therefor. The success of such electronically skilled persons is due in large measure to the fact that the encoded or otherwise obfuscated premium channel signals have been available within the residences of the would-be pirates, so that their activities could be carried out in relative secrecy, and is also due in large measure to the fact that the encoding and obfuscation methods that have been utilized are quite straightforward, such that the encoded or obfuscated signals can easily be synchronized with the circuitry of the television set.
Therefore, another object of the invention is to provide a piracy prevention device and method that avoids delivery of obfuscated premium channel signals that can be easily synchronized to signals generated in a television set in the residence of a person who is not a subscriber to the premium channel service.
It is another object of the invention to provide a piracy prevention device and method that programmably, addressably, irrecoverably obfuscates premium channel signals in a cable television system.